Various proposals have been made in the past for electric-powered vehicles. To date, for a number of reasons, electric vehicle systems have yet to become generally commercially viable for urban and highway applications. There have been proposals to employ zinc-air batteries for urban vehicle propulsion. An example is the publication "Improved Slurry Zinc-Air Systems as Batteries for Urban Vehicle Propulsion," by P. C. Foller, Journal of Applied Electrochemistry, Vol. 16, pp. 527-543 (1986).
Machine Design of Sep. 21, 1989 carried a review of electric batteries and vehicles and found that delivery vans were likely to be the first commercially-produced electrically-driven vehicles.
The Bedford CF electric van, using a lead-acid battery, is in production in the United Kingdom. It has a 50-60 mile range and a top speed of 50 mph, as reported by the Standard Handbook for Electrical Engineers.
Metal-air battery structures are described in the following publications: U.S. Pat. No. 4,842,963, entitled "Zinc Electrode and Rechargeable Zinc-Air Battery;" U.S. Pat. No. 4,147,839, entitled "Electrochemical Cell with Stirred Slurry," U.S. Pat. No. 4,908,281, entitled "Metal-Air Battery with Recirculating Electrolyte;" U.S. Pat. No. 3,847,671, entitled "Hydraulically-Refuelable Metal-Gas Depolarized Battery System;" U.S. Pat. No. 4,925,744, entitled "Primary Aluminum-Air Battery;" U.S. Pat. No. 3,716,413, entitled "Rechargeable Electrochemical Power Supply;" U.S. Pat. No. 4,925,744, entitled "Primary Aluminum-Air Battery."
In U.S. Pat. No. 3,592,698, entitled "Metal Fuel Battery with Fuel Suspended in Electrolyte," there is described inter alia a method for circulating an electrolyte/metal fuel powder mixture through batteries; U.S. Pat. No. 4,126,733, entitled "Electrochemical Generator Comprising an Electrode in the Form of a Suspension" relates to a similar subject, using a circulated suspension of inert cores coated with an electrochemically active material. In U.S. Pat. No. 4,341,847, entitled "Electrochemical Zinc-Oxygen Cell," there is described a method in which an electrolyte is circulated in the annular space between concentric electrodes.
Electrical energy storage systems are described in the following publications: U.S. Pat. No. 4,843,251, entitled "Energy Storage and Supply Battery with Recirculating Electrolyte;" "Energy on Call" by John A. Casazza, et al., IEEE Spectgrum, June 1976, pp. 44-47; U.S. Pat. No. 4,275,310, entitled "Peak Power Generation;" U.S. Pat. No. 4,124,805, entitled "Pollution-Free Power Generating and Peak Power Load Shaving System;" U.S. Pat. No. 4,797,566, entitled "Energy Storing Apparatus."
Regeneration of spent zinc-containing alkaline electrolyte is described in a number of prior patents. For example, in U.S. Pat. No. 3,847,671 (mentioned above), whole spent electrolyte is subjected to electrolysis, when zinc deposited at the cathode is removed with a wiper blade. The thus-removed zinc is said to be substantially heavier than the electrolyte (35-40% KOH) and hence falls to the bottom of each cell. In a particular embodiment, the cathode and anode are specified as being made from copper (or silver-plated copper) and carbon, respectively. In U.S. Pat. No. 3,981,747, it is proposed to regenerate the spent zinc in an alkaline electrolyte by reaction with a strongly electropositive metal, such as magnesium or aluminum, which displaces the zinc. In U.S. Pat. No. 4,341,847 (also mentioned above), spent zinc in the alkaline electrolyte is regenerated either by reversing the current and plating zinc on the anode, or by mechanically replacing zinc oxide particles by active zinc particles, as described e.g. in co-pending U.S. patent application Ser. No. 08/016,019 filed Feb. 10, 1993, (now abandoned) the teachings of which are incorporated herein by reference.
Metal-air and particularly zinc-air battery systems are known in the art and, due to their high energy densities, relative safety of operation and the possibility of ready mechanical recharging, such systems have been suggested as a power source for electrically-propelled automotive vehicles.
In an effort to further increase the advantages of using zinc-air battery systems for electro-automotive propulsion, it has now been proposed to employ a mechanically-rechargeable battery system comprising a rigid anode designed to be rapidly removed and replaced on a periodic basis at dedicated service stations, specifically equipped for the purpose.
Such batteries are described in U.S. patent application Ser. No. 07/964,644, filed Oct. 21, 1992, now allowed and in U.S. patent application Ser. No. 08/002,656, filed Jan. 11, 1993, now allowed, the teaching of both of which are incorporated herein by reference.
In said co-pending applications, there are described improved zinc battery anodes, particularly for zinc-air batteries, featuring a skeletal frame comprising conductive metal having a portion of its surface area formed as open spaces, and an active zinc anode element encompassing the skeletal frame, and said active anode element formed of a slurry of porous granules comprising zinc, impregnated with and suspended in an electrolyte, compacted under pressure onto the skeletal frame.
Said specifications, however, do not teach or suggest a method for automated recharging of such anodes.
As will be realized, in order for such batteries to be commercially viable, it is important that the spent anodic material, which after use has been oxidized, be recycled external to the battery for later re-use in other batteries. To facilitate recycling of the active anodic material, it is necessary to separate the spent anodic material from the other anode components.
In U.S. Pat. No. 5,405,713 FIG. 7 and 8 illustrate the apparatus contemplated and taught at said time for removal of zinc oxide from the anode support frame.
As described therein, zinc, which has been at least partly oxidized, is mechanically removed from the support frame in a machine which is provided with a plurality of axes, each provided with revolvably-driven flexibly-suspended bodies. The machine is provided with means, for example a reciprocable air cylinder, to bring the support frame into contact with the bodies which act to delaminate the relatively brittle zinc oxide from the frame by rotating motion of bodies which angularly strike the anode material as they revolve around the axes to which they are attached.
It has been found, however, that the machine described therein is not sufficiently robust to effect the desired stripping of the discharged anode material from its supporting frame.
As will be realized, because of the mode of interaction, there is mutual abrasion between the anode bed and the revolving bodies. For this reason, metallic bodies could not be used because of problems of contamination of the zinc with other metal impurities.
Similarly, even strong plastic was rapidly eroded by the zinc bed.
Furthermore, there was found to be a conflict between the need to have bodies of sufficient size and mass to deliver significant blows to the rigid static bed of anode material and the stress hinderance between bodies attached to the same axis and effective contact along the entire bed when large bodies were used.
Finally, since the arrangement involved a rotation of 90.degree. between the first contact of a body with the bed of material and the next contact of a second body attached to said same axis with a further area along said bed, the arrangement was found to be time-consuming in operation.
For all of the above reasons, this machine and approach were abandoned for large-scale commercial application.
Said specification also suggested the use of grappling means for pulverizing the discharged anode material. However, the various means tried were found to damage the skeletal frame which was also to be recycled and did not effectively remove the cement-like mass of anodic material from the skeletal frame.
With this state of the art in mind there is now provided according to the present invention a process for removing discharged active zinc-containing material from a mechanically rechargeable zinc battery anode, containing the same, said anode being of the type comprising a skeletal frame, including conductive metal and having a portion of a surface area thereof formed as open spaces, and an active zinc anode component compacted into a rigid static bed of active anode material of tight interparticulate structure encompassing the skeletal frame, and having two opposite major surfaces, said process comprising:
a) introducing said anode in which said active zinc has been at least partly oxidized, between a pair of spaced-apart first and second crusher plates, each of said crusher plates being provided with a plurality of pointed projections of varying heights and a plurality of recesses of varying depths substantially complementary to said projections, said crusher plates being aligned with each other to the effect that tips of projections of said first crusher plate substantially mutually occlude with recesses provided on said second crusher plate and tips of projections of said second crusher plate substantially mutually occlude with recesses provided on said first surface; PA1 b) abruptly reducing the space between adjacent crusher plates while impacting at least indirectly on said anode bed positioned there-between to deform and crack said anode bed; PA1 c) moving said crusher plates away from each other and from said deformed anode bed and then displacing said deformed bed, along at least a first axis, by at least half the distance between adjacent projection tips of at least one of said crusher plates; PA1 d) once again abruptly reducing the space between adjacent crusher plates while impacting on and fragmenting said displaced anode bed; and PA1 e) repeating steps c and d until the fragmentation of said bed and the dislodgement of the resulting fragmented particles from said skeletal frame are achieved. PA1 a) automated means for simultaneously separating a plurality of spent anodes from said casing; said spent anodes comprising support frames to which are attached zinc which has been at least partially oxidized; PA1 b) means for removing used electrolyte from said casing; PA1 c) transport means for conveying spent anodes to an anode processing station; PA1 d) said anode processing station, at which said zinc, which has been at least partly oxidized, is removed from said support frame, said station comprising apparatus for removing discharged active zinc-containing material from said spent anodes, said apparatus comprising a pair of spaced-apart first and second crusher plates, each of said crusher plates being provided with a plurality of pointed projections of varying heights and a plurality of recesses of varying depths substantially complementary to said projections, said crusher plates being aligned with each other to the effect that tips of projections of said first crusher plate substantially mutually occlude with recesses provided on said second crusher plate and tips of projections of said second crusher plate substantially mutually occlude with recesses provided on said first crusher plate, and at least one of said plates is operationally-linked to piston means for affecting abrupt movement between said plates. PA1 e) means for attaching reconstituted active zinc material to a cleaned support frame, comprising a press provided with a container configured to hold said frame immersed in a pre-weighed zinc slurry, said press being provided with means for applying a pressure of at least 20 kg/cm.sup.2 over the surface of said slurry, to form an active zinc anode, having active zinc material compactly pressed to support frame; PA1 f) automated means for simultaneously introducing a plurality of active zinc anodes into said casing; and PA1 g) means for introducing fresh electrolyte into said casing.
The invention also provides apparatus for removing discharged active zinc-containing material from a mechanically rechargeable zinc battery anode, containing the same, said anode being of the type comprising a skeletal frame, including conductive metal and having a portion of a surface area thereof formed as open spaces, and an active zinc anode component compacted into a rigid static bed of active anode material of tight interparticulate structure encompassing the skeletal frame, said apparatus comprising a pair of spaced-apart first and second crusher plates, each of said crusher plates being provided with a plurality of pointed projections of varying heights and a plurality of recesses of varying depths substantially complementary to said projections, said crusher plates being aligned with each other to the effect that tips of projections of said first crusher plate substantially mutually occlude with recesses provided on said second crusher plate and tips of projections of said second crusher plate substantially mutually occlude with recesses provided on said first crusher plate.
Preferably, said apparatus further comprises a pair of spaced-apart elastomeric sheets, each sheet being positioned adjacent one of said crusher plates and defining between themselves a cavity configured to accommodate said anode.
Said elastomeric sheets are preferably made of KOH-resistant material selected from the group consisting of ethylene-propylene polymers, neoprene and nitriles, and said surfaces are preferably made of a material selected from the group consisting of KOH-resistant metal, including nickel and nickel-plated stainless steel, and plastic, selected from the group consisting of polyvinylchloride, polysulfone and polyphenylene oxide.
The invention also provides a refueling system for automated recharging of zinc-air batteries of the type having a plurality of active zinc anode elements formed of active zinc material compactly pressed to a support frame immersed in an aqueous alkaline electrolyte in a battery casing, and of the type described in said aforementioned co-pending application, said system comprising:
The invention will now be described in connection with certain preferred embodiments with reference to the following illustrative figures so that it may be more fully understood.
With specific reference now to the figures in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice .